This invention relates to graders of the type used in earth-working and road-building operations and more particularly to structures for coupling the blade or moldboard of a grader to the vehicle while enabling sideward movement of the blade relative to the blade supports.
The blade or moldboard of a grader is usually coupled to the vehicle through a complex mounting assembly designed to enable the blade to be manipulated and oriented in several different ways relative to the path of travel of the vehicle. One of the blade motions which is usually provided for is a sideward or lateral movement relative to the structure which supports the blade. In order to provide for this sideward movement, it is customary to secure a pair of linear slide rails along the back of the blade. Support brackets carried below the blade circle of the grader have slots into which the slide rails are received. Thus the blade is effectively fastened to the vehicle and carried thereon but may be moved sidewardly by a sliding movement of the rails in the support brackets. Hydraulic actuators or the like are usually present to facilitate the sideward adjustment of the position of the blade in operation.
To prevent wearing of the slot surfaces of the brackets by movement of the rails, many grader constructions utilize some form of wear strips or slide bearings within the bracket slots. Unlike the brackets, which are permanent parts of the vehicle and which are relatively costly, such wear strips can be replaced from time to time when wearing has progressed to the point that the blade is too loosely mounted to enable the desired degree of precision in grading operations. Some blade mounting structures provide for a limited amount of shimming to compensate for wear or for compensation by threaded adjustments which act on the slide bearings but as a practical matter occasional replacement of the wear strips is required. The strong reaction forces which may bear against the blade of a grader in use and the fact that highly abrasive sand or rock particles may often be present in the region of the slide rails contribute to the severity of the wear problem.
Although a variety of wear strips or slide bearings have been developed for this particular purpose, the prior structures exhibit one or more characteristics which it would be desirable to avoid. First, adjustment of the lateral position of the blade and rails may exert strong sideward forces tending to pull the wear strips out of the support bracket slots. To prevent this it has heretofore been necessary to complicate the support structure by providing removable wear strip retainer elements at each side of the brackets to hold the wear strips in place, such fastening means usually being secured in place by bolts or the like. Sideward forces are sufficiently severe that occasional failure of these bolts has been encountered.
In most constructions, a pair of wear strips are required within each bracket and heretofore the two members of each pair have required different configurations. This prevents interchanging of the two wear strips when the wear on one is more pronounced than the wear on the other as is often the case. This has the undesirable effect of shortening the period between replacements. The requirement for two different wear strip configurations may also create a possibility of incorrect orientation during installation and complicates the manufacture and stocking of replacement parts.
Still further, installation of prior wear strip replacements in the field has inherently been a somewhat difficult task, in many cases requiring complete removal of the blade from the grader.